804 ALASKAN GLACIER STUDIES This glacier was mapped by Witherspoon in 1900,1 and is shown with different form in the revised map published in 1909.* It has been seen by the National Geographic Society's expedition only from a distance, and its chief importance in our studies comes in connection with its contribution of outwash to the large valley trains of the Copper and Martin Rivers. Martin River Glacier. Martin River Glacier terminates about 20 miles east of Copper River, and is separated from the sea by the foothill region of the Controller Bay coal field. It is 3 to 5 miles wide, over 25 miles long, and terminates less than 350 feet above sea level. It is larger than Miles Glacier, much larger than Sheridan Glacier, and is the most extensive valley glacier in the Copper River portion of the Chugach Mountains.8 The covering of ablation moraine on the terminus renders the glacier relatively inconspicuous from the Copper River railway, and it would not be noted here were it not for the extensive outwash gravel plain built up by its glacial streams. These coalesce with the Copper River delta on the west, so that Copper River has been pushed to the extreme western edge of its valley. GLACIATION NEAR COPPER RIVER DELTA The varied and interesting features produced by glacial erosion and glacial deposition near the ice tongues described in this chapter are so involved with the other glaciers to be described and with general conditions of glaciation of the Copper River valley, that their treatment is postponed to Chapter XXIII. * Plate n, House Document 546, 66th Congress, 2nd Session, The Geology and Mineral Resources of a Portion of the Copper Eiver District; Alaska, by P. C. Schrader and A. C. Spencer, Washington, 1901. See another arrangement of glaciers here, in the map published as Pl.^XTt, Bull. 284, U. S. Geol. Survey, 1906. «PI. I, Bull. 374, U. S. Geol. Survey. 1909; also Chitina Quadrangle. • This glacier has been described by G.C. Martin. See Bull. 885, U. S. Geol. Survey, 1908, pp. 16, 48-52, 56, 64-65 and Plates I, n and HI. The junior author of this book visited portions of the glacier in 1904.